Lee, Chung, and Lee (2002) show that conversion rate of Chonsei to monthly rent is related to the required rate of return of equity invested in housing. After that, studies on Chonsei have focused on the leverage effect and risk of owners` point of view. This paper insists that Chonsei price is related to risk of tenant as well as risk of owner. In fact, Chonsei contract is similar to the debt contract, especially par bond. To adopt this feature and the risk of tenant, we use option pricing method. As a result, we could show that Chonsei price depends on existence of senior loan that is general wisdom of Chonsei contract. In addition, we could prove that the model is consistent to the empirical evidences; Chonsei price depends on interest rate or the volatility of house price, and conversion rate of Chonsei to monthly rent is positively correlated to the amount of security deposit.